The treatment of cancer by immunization with tumor antigens is a promising new therapeutic approach which lacks the toxicities associated with traditional chemotherapy and radiotherapy (Blattman and Greenberg, Science, 305: 200-205, 2004.) Tumor antigen vaccination stimulates the host's own immune system to generate T cells and antibodies specific for tumor cells. It is being studied in a wide variety of human cancers, owing to the growing list of protein tumor antigens identified (Pardoll, Nat Med, 4: 525-531, 1998; Rosenberg, Immunity, 10: 281-287, 1999; Rosenberg, Nature, 411: 380-384, 2001). One tumor antigen reaching an advanced state of clinical development is the tumor-specific immunoglobulin clonally expressed by B cell lymphomas and related malignancies (Timmerman, Int J Hematol, 77: 444-455, 2003).
The collection of antigenic determinants in the variable region of an immunoglobulin is termed the idiotype (Id), and is unique for each lymphoma. Thus the idiotype of each B cell cancer can serve as a truly tumor-specific antigen, making it an attractive target for immunotherapy. The clonal T cell receptors expressed by T cell lymphomas express analogous structures that can also serve as targets for immunotherapy (Okada et al., J Immunol, 159: 5516-5527, 1997). Tumor-specific Id protein can be derived from individual B cell lymphomas using hybridoma (Levy and Dilley, Proc Natl Acad Sci USA, 75: 2411-2415, 1978) or molecular cloning techniques (Hawkins et al., Blood, 83: 3279-3288, 1994), yielding a custom-made tumor antigen for each patient. Vaccination with tumor-derived Id can potentially elicit a polyclonal antibody response, as well ad CD8+ and CD4+ T cells recognizing Id-derived peptides presented on class I and class II major histocompatibility complex proteins at the tumor cell surface (Timmerman, Int J Hematol, 77: 444-455, 2003; Hurvitz and Timmerman, Expert Opin Biol Ther, 5: 841-852, 2005).
To render this self-derived protein more recognizable to the immune system, Id is usually chemically conjugated to the highly immunogenic carrier protein keyhole limpet hemocyanin (KLH) using glutaraldehyde, as performed in numerous studies in both mouse models (Maloney et al., Hybridoma, 4: 191-209, 1985; Kaminski et al, J Immunol, 138: 1289-1296, 1987; George et al., J Immunol, 141: 2168-2174, 1988; Campbell et al., J Immunol, 139: 2825-2833,1987; Campbell, M. J., et al., J Immunol, 145: 1029-1036,1990; Campbell, et al., J Immunol, 141: 3227-3233, 1988; Kwak, L. W., et al., Proc Natl Acad Sci USA, 93: 10972-10977, 1996; Timmerman, J. M. and Levy, R., J Immunol, 164: 4797-4803, 2000) and humans (Kwak, L. W., et al., N Engl J Med, 327: 1209-1215, 1992; Kwak, L. W., et al., Lancet, 345: 1016-1020, 1995; Hsu, F. J., et al., Nat Med, 2: 52-58, 1996; Hsu, F. J., et al., Blood, 89: 3129-3135,1997; Bendandi, M., et al., Nat Med, 5: 1171-1177,1999; Timmerman, J. M., et al., Blood, 99: 1517-1526., 2002; Barrios, Y., et al., Haematologica, 87: 400-407, 2002; Timmerman, J. M., et al., Blood, 96: 578a, 2000; Timmerman, J., et al., Blood, 98: 341a (abstract#1440), 2001; Redfern, C., et al. Single agent activity of Favid [Id-KLH vaccine] for indolent NHL. Blood, 102: 898a (abstract #3341), 2003; Koc, O., et al. Id/KLH vaccine (Favid™) following treatment with rituximab: An analysis of response rate immprovement (RRI) and time-to-progression (TTP) in follicular lymphoma (FL). Blood, 104: 170a (abstract #587), 2004). Glutaraldehyde primarily cross-links proteins via lysine and cysteine residues, with secondary reactions at tyrosine and histidine (Migneault, I., et al., Biotechniques, 37: 790-796, 798-802, 2004).
The effectiveness of glutaraldehyde-conjugated Id-KLH protein vaccination in several murine lymphoma model systems (Kaminski, M. S., et al., J Immunol, 138: 1289-1296, 1987; George, A. J., et al., J Immunol, 141: 2168-2174, 1988; Campbell, M. J., et al., J Immunol, 139: 2825-2833, 1987) led to its adoption in Id vaccine clinical trials in patients with B cell lymphoma (Timmerman, J. M. and Levy, R. L., Clinical Lymphoma, 1: 129-139, 2000). In phase I/II trials in lymphoma, Id-KLH vaccination has been shown to elicit anti-Id immune responses that correlate with improved progression-free and overall survival, (Kwak, L. W., et al., N Engl J Med, 327: 1209-1215, 1992; Hsu, F. J., et al., Blood, 89: 3129-3135, 1997); clearance of circulating tumor cells from the blood (Bendandi, M., et al., Nat Med, 5: 1171-1177, 1999); and durable tumor regressions (Timmerman, J. M., et al., Blood, 99: 1517-1526, 2002; Redfern, C., et al., Blood, 102: 898a (abstract #3341), 2003; Koc, O., et al., Blood, 104: 170a (abstract #587), 2004). Based on these results, several large phase III clinical trials of Id-KLH vaccination are now underway in North America (Hurvitz, S. A. and Timmerman, J. M., Curr Opin Oncol, 17: 432-440, 2005.). These three trials, sponsored by Genitope (Redwood City, Calif.; WorldWideWeb.genitope.com), U.S. Pat. No. 5,972,334, Favrille (San Diego, Calif.; WorldWideWeb.favrille.com), U.S. Patent Publication US2005/0202004A1, and Accentia (Tampa, Fla.; WorldWideWeb.accentia.net), are all testing the efficacy of glutaraldehyde-conjugated Id-KLH co-administered with the cytokine granulocyte-macrophage colony stimulating factor (GM-CSF) after standard cytoreductive therapy.
Idiotype vaccination has shown promising results in phase I/II trials for non-Hodgkin's B cell lymphomas, and glutaraldehyde Id-KLH vaccines are now being formally evaluated for efficacy in several phase III clinical trials (Hurvitz, S. A. and Timmerman, Curr Opin Oncol, 17: 432440, 2005). Nonetheless, current Id-KLH vaccines remain far from optimal, as they fail in many patients to induce anti-Id immune responses, tumor regression, or prolonged survival. Glutaraldehyde Id-KLH conjugates fail to elicit anti-Id immune responses in up to one-half of vaccinated patients (Hsu, F. J., et al., Blood, 89: 3129-3135, 1997; Timmerman, J. M., et al., Blood, 96: 578a, 2000; Redfern, C., et al., Blood, 102: 898a (abstract #3341), 2003; Koc, O., et al., Blood, 104: 170a (abstract #587), 2004). Moreover, in some murine lymphoma models (A20), glutaraldehyde Id-KLH vaccines have been reported to lack anti-tumor efficacy (Biragyn, A. and Kwak, L. W. Models for Lymphoma. In: A. M. K. J. E. Coligan, D. H. Margulies, E. M. Shevach, W. Strober, and R. Coico, editors. (ed.), Current Protocols in Immunology, pp. 20.26.21-20.26.30. Hoboken, N.J.: John Wiley & Sons, Inc., 2001). Current clinical trials using glutaraldehyde to conjugate patient Id proteins to KLH may be limiting the effectiveness of the vaccines by over cross-linking the proteins.
Vaccines using other linking approaches would be desirable, with respect to both cancer vaccines and vaccines against other pathogens. Heterobifunctional cross-linking agents containing malemide have been used to link (1) enzymes or toxind to antibodies and antibody fragments and (2) peptides to proteins. (Hashida et al., J Appl Biochem, 6: 56-63, 1984; Peeters et al., J Immunol Methods, 120: 133-143, 1989; Yoshitake et al., J Biochem (Tokyo), 92: 1413-1424, 1982; Yoshitake et al., Eur J Biochem, 101: 395-399, 1979). These methods generate a thio ether bond, which are disclosed in the art to be non-cleavable.